In many processes using a stirred vessel, heat is transferred from the vessel fluid to a secondary fluid flowing through vertical pipes which baffle the vessel fluid. These vertical pipe-coil baffles serve as both mixing baffles, to prevent vortex formation about a rotating agitator used to stir the vessel fluid, and provide heat transfer surface area. There are numerous process applications for vertical pipe-coil baffles.
A major disadvantage to vertical pipe-coil baffles is the lack of provision for thermal expansion to accommodate larger temperature differential applications between the pipe coil fluid and the mixing vessel fluid. Thermal expansion and contraction are very significant problems where long tubes are used especially tubes arranged in a single pass tube bundle. In such tube bundles, the inlet and outlet headers are susceptible to stress cracking. Thermal expansion stresses are lower in U-tube bundles but the design is not very compact, limiting the heat transfer surface area available for a tube bundle of fixed external dimensions. "U" tube bundles also have a relatively poor heat exchange coefficient and require a complex manifold arrangement.
A tube bundle designed to overcome thermal expansion problems, especially an agitated mixing vessel, would be very desirable.